This invention relates to a method of hardening wooden flooring blanks in bundles in such a manner as to permit easy separation of the blanks after the hardening processing is completed. The invention has application in the production of hardwood flooring, such as slats, planks and parquet blocks, out of hardwoods such as oak and maple. Finished hardwood flooring products of this type are typically installed by embedding the individual strips or blocks in a mastic-type adhesive on a subfloor.
The invention can be used with solid wood and with thin veneers of such woods. For purposes of illustrating the invention of this application, principal emphasis will be placed on the method of hardening veneers of oak and maple, although other species of wood can be treated, as well.
Applicant's process of manufacturing hardwood flooring includes the steps of forming veneers of about 1/10 inch in thickness, and then adhering the veneer strips to spaced-apart backing blocks or to solid core materials. The side-to-side spaces between the adjacent blocks provide flexibility to the finished flooring strip while permitting the use of inferior grades of wood for the hidden base portions of the product. The veneer surfaces are substantially blemish-free and when finished form the exposed, decorative surface.
The attractiveness and wear resistance of the flooring strips can be enhanced by hardening the veneers before adhering them to the backing blocks. This process involves forming a closely and densely-stacked bundles of veneer blanks which are loaded into a reactor vessel where the blanks are exposed to a solution containing monomethylmethacrylate ("MMA"). Bundling of the blanks greatly increases the quantity of blanks which can be processed during a single cycle.
Vacuum and pressure conditions are used to impregnate the MMA into the cell structure of the blanks. When cured, the blank is substantially more wear and damage resistant without affecting the attractiveness, natural appearance and other desirable characteristics of the product. Dyes may be used during this process to achieve desired finish colors in the blanks.
One problem observed during this process is the tendency of the blanks to stick together so that they must be manually separated. This causes damage to the surface and renders the blank unsuitable for use. In addition, hardening the blanks while bundled can also cause warping and splitting. These problems occur variably, but tend to be more pronounced with maple than with oak--two common hardwood flooring woods.
One procedure which reduced the sticking somewhat was sandwiching alternate blanks of oak and maple in the bundle, since oak and maple tends to stick to itself more readily than to each other. However, alternating the blanks and then separating them back into respective sets of oak and maple blanks is very labor intensive, and creates difficulties in producing the proper proportions of oak and maple in needed colors.
It has been determined that the use of Polyethylene Glycol ("PEG") in a blend with the MMA substantially reduces the tendency of the flooring blanks to stick together during the hardening process. The process also enhances the stability of the blanks, thus reducing the tendency of the blanks to crack, warp, split, cup and crown.